The present invention relates to extraction of granulocyte/macrophage colony stimulating factor (GM-CSF) from GM-CSF-expressing bacteria.
Granulocyte/macrophage colony stimulating factor is believed to be a potential therapeutic agent against infection and cancer. Clinical testing and widespread use of GM-CSF have been delayed owing to the unavailability of sufficient quantities of the material and the great expense of obtaining GM-CSF from natural sources. Recombinant DNA techniques have been used to create bacteria capable of expressing GM-CSF; see, for example, DeLamarter et al., EMBO J., Vol. 4, 2575-2581 (1985). Fermentation of such bacteria is expected to yield sufficient quantities of GM-CSF at substantially lower cost than would be possible utilizing natural sources of GM-CSF. However, clinical use of GM-CSF also requires high purity material that is not contaminated by cell constituents or cell debris of the GM-CSF-expressing bacteria. Contamination by such impurities could result in adverse reactions or in test results that are not reproducible. Accordingly, extraction of GM-CSF from the cells of GM-CSF-expressing bacteria in sufficiently high purity and yield for clinical use has been a major problem.